No. People are called to pray as they feel led. Some will pray out loud, some will pray quietly by themselves. Some will receive prayer from others, some will just be.
Many of us, especially those who are early in our faith growth, may be anxious about gathering together for prayer. We may not know how to pray, do not pray regularly, feel fearful of praying out loud and if we are honest with ourselves, may not even believe prayer works. Some may hear others praying out loud with authority, feel that they cannot do the same and again, if we are honest with ourselves, begin to feel "not good enough." Who wants to be a part of that?
The point is not to pray out loud but for the people of God to intentionally gather, collectively orient our hearts to God, wait on Him and see what happens. Simply doing that, and sacrificing our time to do so, is prayer.